The invention relates to a subscriber identity module (SIM) card for mobile telephones and, in particular, to the storage of directory entries on the SIM card for mobile telephones.
The number of directory entries in mobile telephones is constantly increasing because of the rising capacity of SIM cards. Thus, at present, it is possible to store up to 255 entries in an abbreviated dialing number (ADN) field or a fixed dialing number (FDN) field of the SIM card. However, it is not possible to store the directory entries in a hierarchical structure in the directories of current SIM cards, that is to say to organize the entries in various levels. The data structure of the SIM card including the definition of the ADN and FDN data records is, for example, explained in global system for mobile communications (GSM) specification 11.11, version 5.0.0 dated December 1995.
Telephones which organize their entries hierarchically, that is to say permit several telephone numbers per entry, or else assign only to that entry an identifier such as, for example, office or FAX therefore store this information not on the SIM card but in the telephone set itself. As a result, serious problems arise when the card is switched to other telephones that do not support the structure. For example, changing the memory location number in another telephone can lead to a false allocation of the identifier to a number when the SIM card is read by the telephone which contains the designations of the individual numbers.
It is accordingly an object of the invention to provide a SIM card with directory entries for mobile telephones which overcomes the above-mentioned disadvantages of the prior art devices of this general type, which has a data structure that permits a hierarchical directory, and the SIM card and its data structure being downwardly compatible.
With the foregoing and other objects in view there is provided, in accordance with the invention, a subscriber identity module (SIM) card for mobile telephones. The SIM card contains a memory programmed with extension data records, further data structures defining a hierarchical order of telephone entries, and initial data records corresponding to a global systems for mobile communications (GSM) specification for storing the telephone entries. The initial data records are selected from the group consisting of a field of abbreviated dialing number (ADN) data records and a field of fixed dialing number (FDN) data records. Each of the initial data records contains a sector which can reference one of the extension data records such that it is possible to form an ordered chain of the extension data records referencing one another. Each of the extension data records are formed of three sectors including an identifier sector having an identifier for identifying a respective extension data record as a hierarchical extension data record. In turn, the hierarchical extension data record references at least one of the further data structures.
The SIM card according to the invention for mobile telephones contains a field of ADN and/or FDN data records, corresponding to the GSM specification for storing telephone entries, an ADN data record (FDN data record) containing a sector which references a first extension data record. In the simplest case, the first extension data record, contains three sectors, and has in its first sector an identifier which identifies it as a xe2x80x9chierarchicalxe2x80x9d data record, and the extension data record refers to one or more further data structures which define the hierarchical order of the telephone entries. It is also possible for the first extension data record still not to be a hierarchical data record. In this case, the first extension record refers to a further second extension data record which is identified as xe2x80x9chierarchicalxe2x80x9d by its first sector. Further following extension data records which relate, possibly via a chain of extension data records, to the first xe2x80x9chierarchicalxe2x80x9d extension data record, are likewise of xe2x80x9chierarchicalxe2x80x9d type. Expressed in general terms, the interlinking may be explained as follows: there can be a sequence of N extension data records for an ADN or FDN data record of an appropriate field, N being a natural number greater than zero, such that an nth extension data record with n xcex5{0, . . . , Nxe2x88x92l} references the (n+1)th extension data record, the data record for n=0 being identical with the ADN or FDN data record, at least a kth extension data record with kxcex5{1, . . . , N} being identified as hierarchical extension data record, and all further jth extension data records with jxcex5{k+1, . . . , N} likewise being xe2x80x9chierarchicalxe2x80x9d extension data records.
The hierarchical extension data record has an identifier sector, an extension data sector and a reference sector. In this case, the extension data sector is constructed from the subsectors type field, reference or link field and a further third sector. The link field contains a predetermined number of subaddresses, each subaddress referring to a further data structure, and the type of the subaddress being fixed by the type field. The extension data sector preferably contains the subsector type field with a length of 2 bytes, 8 subaddresses with a length of 1 byte in each case, and a subsector, which is reserved for later use, with a length of 1 byte.
The further data structures contain at least one subnumber field and/or one group field. A data record of the subnumber field contains an identifier of the number type and a number. A data record of a group field contains an identifier of the group name and a reference sector, a reference sector a referring to an overgroup.
Depending on the type of subaddress, the subaddress containing a reference and fixed by the type field refers to a data record of a subnumber field or to that of a group field.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a SIM card with directory entries for mobile telephones, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.